The goal of this proposal is to elucidate the genetic variability within the regulatory region of the human immunodeficiency virus 1 (HIV-1) long terminal repeat (LTR) in infected individuals and to understand how this variability may influence HIV-1 pathogenesis. After infection by HIV-1 a period of unpredictable length is established of viral latency or persistency during which there are few, if any, ill effects. Our hypothesis is that variability in the arrangement and sequence of cis- acting regulatory elements within the HIV-1 LTR can influence replication of the virus, thus affecting the progression of AIDS. Such cis-element effects on retroviral disease progression have been well established in studies of murine leukemia viruses. We propose to identify the in vivo sequence variation in the HIV-1 LTR regulatory region by molecular cloning and DNA sequence analysis of this region after direct polymerase chain reaction (PCR) amplification of DNA from infected individuals. Such an approach has already identified a "hot spot" for tandem sequence duplications within the HIV-1 LTR just upstream of the enhancer core elements. The activity of altered HIV-1 regulatory regions will be assayed by transient transfection assays and by infection with recombinant HIV-1 virus. The activity of individual elements identified by sequence rearrangement will be assayed by construction of multimerized synthetic enhancers. Lastly, the patterns of expression of cellular factors that interact with individual HIV-1 regulatory elements will be characterized. This proposal forms a multifaceted experimental approach to an understanding of how sequence variation, within the HIV-1 LTR, in particular sequence duplications, may influence the course of AIDS. It is our view that ultimately it may be possible to establish correlations between different HIV-1 LTR variants and viruses that establish short or long latency or persistency periods before the onset of overt clinical symptoms and therefore to predict the course of disease progression.